Analysis of new biomarker for evaluation of SLE activity with autoantibody penetration to cells

系统性红斑狼疮(SLE)涉及多种自身抗体，可能与组织损伤有关。活动期SLE患者的免疫球蛋白G(Ig G)，尤其是抗DNA Ig G在体外具有穿透外周血单核细胞的能力。穿透的靶细胞是循环中的CD8(+)T细胞、B细胞、NK细胞、单核细胞、树突状细胞(DC)。抗Fc抗体不能抑制抗DNA抗体进入细胞，但甲基β-环糊精、RAFT/小窝抑制剂或DNA抗原的共存可阻断这种内化。免疫荧光研究表明，抗DNA免疫球蛋白利用RAFT/Caveolae进入细胞，分布在溶酶体中，但在细胞核中未检测到。这种穿透作用改变了免疫细胞的生物学功能。也就是说，纯化的抗DNA免疫球蛋白诱导人单核细胞来源的树突状细胞成熟和激活，CD83上调，IL-12分泌增加，混合淋巴细胞反应中同种异体或自体T细胞对DC的刺激增强。我们的结果为抗DNA自身抗体在细胞功能中的作用提供了新的视角，如成熟和产生几种类似细胞因子的蛋白质，并可能解释SLE患者外周耐受被打破的新机制。

Systemic lupus erythematosus (SLE) involves a variety of autoantibodies which may be responsible for the tissue injury. Immunoglobulin G (IgG), especially anti-DNA IgG from active SLE had an ability to penetrate into peripheral blood mononuclear cells in vitro. The target cells for the penetration are CD8 (+) T cells, B cells, NK cells, monocytes, dendritic cells (DC) in circulation. Anti-Fc antibodies failed to cause the inhibition of anti-DNA IgG penetration into cells, but the coexistence of methyl beta cyclodextrin, raft/caveolae inhibitor, or DNA antigen blocked the internalization. Immunofluorescence studies revealed that anti-DNA IgG used raft/caveolae for their entry into the cells, and were distributed in lysosome, but not detected in the nuclei. The penetration caused to alter the biological function of the immunocytes. Namely, purified anti-DNA IgG induced the maturation and activation of human monocyte-derived dendritic cell as observed by CD83 up-regulation, IL12 secretion and an enhanced stimulation of allogenic or autologus T cells to DC at mixed lymphocyte reaction. Our results provide a new sight for the role of anti-DNA autoantibodies at cell function such as maturation and production of several proteins like cytokines, and may explain a novel mechanism where peripheral tolerance is broken in SLE patients.